Stridor

Stridor is a high-pitched sound that is usually heard best when a child breathes in (inspiration). It is usually caused by an obstruction or narrowing in your child’s upper airway. The upper airway consists of the following structures in the upper respiratory system:

Nose

Nasal cavity or passage

Sinuses: cavities, or air-filled pockets, that are near the nasal passages. They include:

Sthmoid sinus: located inside the face, around the area of the bridge of the nose. This sinus is present at birth and continues to grow until puberty.

Maxillary sinus: located inside the face, around the area of the cheeks. This sinus is also present at birth and continues to grow until puberty.

Frontal sinus: located inside the face, in the area of the forehead. This sinus does not develop until around seven years of age.

Sphenoid sinus: located deep in the face, behind the nose. This sinus does not fully develop until adolescence.

Larynx: also known as the voice box, the larynx is a cylindrical grouping of cartilage, muscles, and soft tissue which contains the vocal cords. The vocal cords are the upper opening into the windpipe (trachea), the passageway to the lungs.

Trachea (windpipe): a tube that extends from the voice box to the bronchi in the lungs.

The sound of stridor depends on the location of the obstruction in the upper respiratory tract. Sometimes, the stridor is heard when the child breathes in (inspiration) and can also be heard when the child breathes out (expiration).

What causes stridor?

Stridor can be caused by diseases or problems with the anatomical structure of the child’s airway. The upper airway in children is shorter and narrower than that of an adult and therefore more likely to lead to problems with obstruction.

Here are the most common causes of stridor:

Congenital causes (problems present at birth):

Laryngomalacia: parts of the larynx (voice box) are floppy and collapse causing partial airway obstruction. The child will usually outgrow this condition by the time he/she is 18 months old. Some children may need surgery.

Subglottic stenosis: a condition in which the larynx (voice box) becomes too narrow in an area called the subglottic space (the area below the vocal cords). Children with subglottic stenosis are usually diagnosed a few months after birth especially if the airway becomes stressed by a cold or other virus. Children may eventually outgrow sublottic stenosis without treatment, but most children with a severe obstruction will need surgery.

Subglottic hemangioma: a mass made of blood vessels. It is similar to a strawberry birthmark. Subglottic hemangioma grows quickly in the child’s first few months of life; signs are usually obvious between ages three to six months. Some children outgrow this problem as the hemangioma begins to get smaller after the first year of life. If the obstruction is severe, the child will need surgery.

Vascular rings: occurs when the trachea (windpipe) is completely enclosed by an artery or vein inside the chest. Surgery may be needed.

Infectious causes:

Croup: an infection caused by a virus that leads to swelling in the airways, especially in the subglottic space (the area below the vocal cords). Croup causes breathing problems and is caused by a variety of different viruses, most commonly the parainfluenza virus.

Epiglottitis: an acute life-threatening bacterial infection that causes swelling and inflammation of the epiglottis (an elastic cartilage structure at the root of the tongue that helps to prevent food from entering the windpipe during swallowing). Epiglottis causes breathing problems that can progressively worsen. Epiglottis may lead to airway obstruction (a medical emergency) if there is so much swelling that air cannot get in or out of the lungs. Epiglottitis is usually caused by the bacteria Haemophilus influenzae. It is now rare because children are routinely vaccinated against this bacteria.

Bronchitis: an inflammation of the breathing tubes called bronchi. Bronchitis causes increased production of mucus and other changes. Acute bronchitis is usually caused by infectious agents such as bacteria or viruses. It may also be caused by physical or chemical agents–dusts, allergens, strong fumes–and those from chemical cleaning compounds or tobacco smoke.

Severe tonsillitis: an inflammation of the tonsils, the small, round pieces of tissue that are located in the back of the mouth on the side of the throat. Tonsils help fight infections by producing antibodies. Tonsils can be seen by shining a light in the throat.

An abscess in the throat: a collection of pus surrounded by inflamed tissue. If the abscess is large, it may narrow the airway critically. These abscesses may be located next to the tonsil or in the soft tissue of the neck surrounding the airway.

Traumatic causes:

Foreign bodies: objects placed in the mouth that do not belong there. For example, a peanut in the trachea (windpipe) may close off breathing passages and result in suffocation and death.

Fractures in the neck

Swallowing a harmful substance (such as acid, lye)

How do you diagnose stridor?

We can usually diagnose stridor with just a medical history and physical examination. Remember, stridor is a symptom of some underlying problem or condition. Your child’s physician may order some of the following tests to determine the cause of the stridor:

Blood tests

Pulse oximetry: a test that uses a small machine (oximeter) to measure the amount of oxygen in the blood. During pulse oximetry, a small sensor (like a Band-Aid) is taped onto the child’s finger or toe. When the machine is on, a red light can be seen in the sensor. The sensor is painless, and the red light does not get hot.

Sputum culture: a diagnostic test performed on the material that is coughed up from the lungs and into the mouth. A sputum culture can determine if an infection is present.